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Happy New Year!
Unfortunately, the year does not appear to be off to a good start for our wintering whooping cranes. As I’m sure you know, a whooping crane was found dead in Aransas Bay along San Jose Island in Sand Lake.
Do you know how many whoopers have been found dead in the recent past? Does anyone maintain a data base which records the cause of death?
My thought, as you know from our pervious discussion, is we should combine our resources to produce educational material to help people respect and protect whooping cranes.
I hope you are doing well.
San Antonio Bay Foundation
Best Wishes for the New Year.
It is very sad to begin the New Year with news that a Whooping Crane was found dead and that its potential cause of death is being investigated. When a wild population is as low as the Whooping Crane’s is, at just over 300 individuals, it is difficult to learn about the mortality of even a single individual. It is also a sad situation to learn that this may be just one more case of many in the last few years, where a Whooping Crane has been found dead as a result of it being killed intentionally or unintentionally by humans. I am not aware of any formal database that keeps records of Whooping Crane mortality, however, USFWS region 4 has kept track of Whooping Crane deaths that have not been due to natural causes. It is very unfortunate, because if we include Whooping Crane known mortalities from the reintroduced populations in the eastern U.S. and Louisiana, this latest incident is not an isolated one. There have been at least 21 recorded incidents since 2010 involving Whooping Crane mortalities attributable to humans. Some incidents involve more than one Whooping Crane, so the actual number of known Whooping Crane mortalities is at least 29 so far. It is troubling to me to know that so many Whooping Cranes have died not due to natural causes. And it is also troubling to think that those that have been discovered and that we know about may not be all the incidents that have occurred throughout North America.
As the Whooping Crane wintering range in Texas continues to expand outside the boundaries of protected areas we should all be more vigilant and try to do what we can to ensure the protection and long-term survival of this species. So I agree with you, that all of us interested in the conservation of Whooping Cranes should be very concerned about this trend in Whooping Crane mortalities. We should also all be willing to work together to develop a strategy that may include the production of educational material to help people learn how to protect Whooping Cranes that our outside the protected boundaries of the Aransas National Wildlife Refuge. While some past incidents are known to be the result of vandalism some incidents may be legitimate accidents involving lack of information of Whooping Crane presence in an area and/or not being able to identify a Whooping Crane. Some states require hunters who will be hunting in areas with potential presence of Whooping Crane to view a short online presentation to make them aware of the presence of Whooping Cranes and how to identify them so they are not shot accidentally. I hope all the organizations and agencies interested in Whooping Cranes can come together to discuss and work in collaboration to develop a strategy for education and protection of Whooping Cranes outside protected areas.
QUESTION: Hi Felipe! 3 degrees in Bozeman, Montana right now – was 45 this morning! Nice to connect with you after meeting you at Pop’s Place. I know we discussed this last March, but can you please enlighten us as to what the wild whoopers eat in the great north areas like Wood Buffalo during the summer? Fascinating subject. –Karin
It is nice to hear from you. I hope you are staying warm in Montana.
There are several food items that have been recorded for Whooping Cranes in migration in the northern Great Plains. Although, I should mention that there is no specific study to date that has conducted a systematic study of Whooping Crane diet item in the migratory corridor or the Breeding grounds. Most observations are based on opportunistic sightings. The reason I mention this before including the list of known food items is that the list is likely to be incomplete and some items consumed are not reported yet and others items that are reported could be relatively rare but were observed at some point. Much of what is assumed to be Whooping Crane food items is more related to the potential feeding site than actual observation of consumption of a food item. That is people have visited a place where a Whooping Crane was observed then searched the area for potential prey items and assumed they could be consumed. There are clear problems with this approach as for example in the wintering grounds, small fish are the most abundant “potential” food item in feeding locations of Whooping Cranes, but fish in general make up an extreme low number of prey items and biomass in studies of winter food items. Some of the prey items observed to have been consumed by cranes in the northern Great Plains include amphibians (frogs, toads, salamanders, and frog egg masses), reptiles (unidentified snakes), fish (chad?), mammals (unidentified rodents), invertebrates (including earthworms, crayfish, beetles, and unidentified insects) waste corn and other grains, and other unidentified vegetation. While no diet or foraging study exists from the breeding grounds potential food items in nesting grounds, determined by examining ponds where cranes where observed feeding, include: frogs, mice, voles, flightless birds, reptiles, dragonflies, damselflies, crayfish, clams, aquatic tubers, berries, grasshoppers and crickets. In Wood Buffalo National Park in the Northwest Territories of Canada chicks are known to be fed significant numbers of dragonfly larvae.
It is important to note that while we know of a number of food items that Whooping Crane eat in the northern part of their range some of the items on the list are presumed to be prey items based on the observations of feeding sites and may not be correct. I think your question is very important because the complete answer to it highlight the fact that our knowledge of Whooping Crane diet and foraging behavior in the northern part of its range is incomplete and still requires significant observation and study to determine with better certainty.
QUESTION: What role do cranes play in the ecology of wetlands? Or what is their function/contribution to wetland ecology. Thanks! Chuck
First of all let me say that in general any organism present in a particular ecosystem, including cranes, would be part of the system’s trophic structure which will include energy and nutrient flows. This means that all organisms serve as both predator and prey of their system, they eat several items and they are in turn consumed and/or broken down by other organisms. In the case of cranes, their specific function or contribution to wetland ecology would be determined primarily by their diet. While most cranes could be considered omnivorous because they eat both plants and animal prey, when the diet is broken down into specific amounts of different food items they tend to be primarily herbivorous, like the Sandhill Crane, or primarily carnivorous like the Whooping Crane. In the case of Sandhill Cranes that roost and rest in wetlands in between foraging bouts, they are depositing nutrients and other items from areas sometimes tens of miles away from the resting and roosting wetlands. Sandhill Cranes can fly up to 10 miles from their roosting wetlands to foraging areas. But in an area of Northern Mexico some cranes fly as much as 20 miles to foraging areas. The amount of nutrient or other item transfer by a single crane may seem insignificant until you consider that some roosting wetlands in Texas and Northern Mexico can have between 10,000 and 30,000 Sandhill Cranes roosting there.
In the case of Whooping Cranes in the wintering grounds, where we have the most detailed information from, they serve in the nutrient and energy flow of the coastal wetlands. Again it becomes a matter of scale and what seems insignificant can be important within the system. For example, I have estimated that in some winters when blue crab are abundant a single Whooping Crane can consume more than seven blue crabs per hour which if translated into approximately 11 hours of foraging during a day equals 77 crabs per day. If you sum all the potential consumption by all the Whooping Cranes present in the wintering grounds the amount of matter and energy flow begins to become significant. In the case of Whooping Crane I also believe they serve as significant seed dispersal agent of wolfberry on the Texas coast which they consume in significant quantities when available from October through December. Because Whooping Crane digestive system is more adapted to feeding on animal matter which can be broken down chemically, they do not break down tough plant matter significantly (like Sandhill Cranes do which have system well adapted to breaking down tough plant matter mechanically). So the vast majority of seeds pass through the digestive tract intact. I have conducted germination trials on wolfberry seeds from Whooping Crane feces and have had up to 100% germination rates. This is very significant because when I did germination trials on seeds contained within the fruit itself and found that sometimes there was no germination (0%) at all. I have also sampled for wolfberry plants through many coastal wetlands from Texas to Florida and the distribution and densities of wolfberry plants is significantly greater in the Whooping Crane wintering grounds than any other wetland we sampled. The Whooping Crane may be improving its own food base for the future by dispersing wolfberry seeds, but more wolfberries also means more food for the many other organisms, birds and mammals as well that feed on this fruit. So the Whooping Crane may not be just participating in energy and nutrient flow in the coastal wetlands it may be modifying it to some extent by changing the distribution and amount of an important food item of the system.